root/drivers/misc/vmw_vmci/vmci_doorbell.c

DEFINITIONS

1. vmci_dbell_get_priv_flags
2. dbell_index_table_find
3. dbell_index_table_add
4. dbell_index_table_remove
5. dbell_link
6. dbell_unlink
7. dbell_notify_as_guest
8. dbell_delayed_dispatch
9. vmci_dbell_host_context_notify
10. vmci_dbell_register_notification_bitmap
11. dbell_fire_entries
12. vmci_dbell_scan_notification_entries
13. vmci_doorbell_create
14. vmci_doorbell_destroy
15. vmci_doorbell_notify

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * VMware VMCI Driver
   4  *
   5  * Copyright (C) 2012 VMware, Inc. All rights reserved.
   6  */
   7 
   8 #include <linux/vmw_vmci_defs.h>
   9 #include <linux/vmw_vmci_api.h>
  10 #include <linux/completion.h>
  11 #include <linux/hash.h>
  12 #include <linux/kernel.h>
  13 #include <linux/list.h>
  14 #include <linux/module.h>
  15 #include <linux/sched.h>
  16 #include <linux/slab.h>
  17 
  18 #include "vmci_datagram.h"
  19 #include "vmci_doorbell.h"
  20 #include "vmci_resource.h"
  21 #include "vmci_driver.h"
  22 #include "vmci_route.h"
  23 
  24 
  25 #define VMCI_DOORBELL_INDEX_BITS        6
  26 #define VMCI_DOORBELL_INDEX_TABLE_SIZE  (1 << VMCI_DOORBELL_INDEX_BITS)
  27 #define VMCI_DOORBELL_HASH(_idx)        hash_32(_idx, VMCI_DOORBELL_INDEX_BITS)
  28 
  29 /*
  30  * DoorbellEntry describes the a doorbell notification handle allocated by the
  31  * host.
  32  */
  33 struct dbell_entry {
  34         struct vmci_resource resource;
  35         struct hlist_node node;
  36         struct work_struct work;
  37         vmci_callback notify_cb;
  38         void *client_data;
  39         u32 idx;
  40         u32 priv_flags;
  41         bool run_delayed;
  42         atomic_t active;        /* Only used by guest personality */
  43 };
  44 
  45 /* The VMCI index table keeps track of currently registered doorbells. */
  46 struct dbell_index_table {
  47         spinlock_t lock;        /* Index table lock */
  48         struct hlist_head entries[VMCI_DOORBELL_INDEX_TABLE_SIZE];
  49 };
  50 
  51 static struct dbell_index_table vmci_doorbell_it = {
  52         .lock = __SPIN_LOCK_UNLOCKED(vmci_doorbell_it.lock),
  53 };
  54 
  55 /*
  56  * The max_notify_idx is one larger than the currently known bitmap index in
  57  * use, and is used to determine how much of the bitmap needs to be scanned.
  58  */
  59 static u32 max_notify_idx;
  60 
  61 /*
  62  * The notify_idx_count is used for determining whether there are free entries
  63  * within the bitmap (if notify_idx_count + 1 < max_notify_idx).
  64  */
  65 static u32 notify_idx_count;
  66 
  67 /*
  68  * The last_notify_idx_reserved is used to track the last index handed out - in
  69  * the case where multiple handles share a notification index, we hand out
  70  * indexes round robin based on last_notify_idx_reserved.
  71  */
  72 static u32 last_notify_idx_reserved;
  73 
  74 /* This is a one entry cache used to by the index allocation. */
  75 static u32 last_notify_idx_released = PAGE_SIZE;
  76 
  77 
  78 /*
  79  * Utility function that retrieves the privilege flags associated
  80  * with a given doorbell handle. For guest endpoints, the
  81  * privileges are determined by the context ID, but for host
  82  * endpoints privileges are associated with the complete
  83  * handle. Hypervisor endpoints are not yet supported.
  84  */
  85 int vmci_dbell_get_priv_flags(struct vmci_handle handle, u32 *priv_flags)
  86 {
  87         if (priv_flags == NULL || handle.context == VMCI_INVALID_ID)
  88                 return VMCI_ERROR_INVALID_ARGS;
  89 
  90         if (handle.context == VMCI_HOST_CONTEXT_ID) {
  91                 struct dbell_entry *entry;
  92                 struct vmci_resource *resource;
  93 
  94                 resource = vmci_resource_by_handle(handle,
  95                                                    VMCI_RESOURCE_TYPE_DOORBELL);
  96                 if (!resource)
  97                         return VMCI_ERROR_NOT_FOUND;
  98 
  99                 entry = container_of(resource, struct dbell_entry, resource);
 100                 *priv_flags = entry->priv_flags;
 101                 vmci_resource_put(resource);
 102         } else if (handle.context == VMCI_HYPERVISOR_CONTEXT_ID) {
 103                 /*
 104                  * Hypervisor endpoints for notifications are not
 105                  * supported (yet).
 106                  */
 107                 return VMCI_ERROR_INVALID_ARGS;
 108         } else {
 109                 *priv_flags = vmci_context_get_priv_flags(handle.context);
 110         }
 111 
 112         return VMCI_SUCCESS;
 113 }
 114 
 115 /*
 116  * Find doorbell entry by bitmap index.
 117  */
 118 static struct dbell_entry *dbell_index_table_find(u32 idx)
 119 {
 120         u32 bucket = VMCI_DOORBELL_HASH(idx);
 121         struct dbell_entry *dbell;
 122 
 123         hlist_for_each_entry(dbell, &vmci_doorbell_it.entries[bucket],
 124                              node) {
 125                 if (idx == dbell->idx)
 126                         return dbell;
 127         }
 128 
 129         return NULL;
 130 }
 131 
 132 /*
 133  * Add the given entry to the index table.  This willi take a reference to the
 134  * entry's resource so that the entry is not deleted before it is removed from
 135  * the * table.
 136  */
 137 static void dbell_index_table_add(struct dbell_entry *entry)
 138 {
 139         u32 bucket;
 140         u32 new_notify_idx;
 141 
 142         vmci_resource_get(&entry->resource);
 143 
 144         spin_lock_bh(&vmci_doorbell_it.lock);
 145 
 146         /*
 147          * Below we try to allocate an index in the notification
 148          * bitmap with "not too much" sharing between resources. If we
 149          * use less that the full bitmap, we either add to the end if
 150          * there are no unused flags within the currently used area,
 151          * or we search for unused ones. If we use the full bitmap, we
 152          * allocate the index round robin.
 153          */
 154         if (max_notify_idx < PAGE_SIZE || notify_idx_count < PAGE_SIZE) {
 155                 if (last_notify_idx_released < max_notify_idx &&
 156                     !dbell_index_table_find(last_notify_idx_released)) {
 157                         new_notify_idx = last_notify_idx_released;
 158                         last_notify_idx_released = PAGE_SIZE;
 159                 } else {
 160                         bool reused = false;
 161                         new_notify_idx = last_notify_idx_reserved;
 162                         if (notify_idx_count + 1 < max_notify_idx) {
 163                                 do {
 164                                         if (!dbell_index_table_find
 165                                             (new_notify_idx)) {
 166                                                 reused = true;
 167                                                 break;
 168                                         }
 169                                         new_notify_idx = (new_notify_idx + 1) %
 170                                             max_notify_idx;
 171                                 } while (new_notify_idx !=
 172                                          last_notify_idx_released);
 173                         }
 174                         if (!reused) {
 175                                 new_notify_idx = max_notify_idx;
 176                                 max_notify_idx++;
 177                         }
 178                 }
 179         } else {
 180                 new_notify_idx = (last_notify_idx_reserved + 1) % PAGE_SIZE;
 181         }
 182 
 183         last_notify_idx_reserved = new_notify_idx;
 184         notify_idx_count++;
 185 
 186         entry->idx = new_notify_idx;
 187         bucket = VMCI_DOORBELL_HASH(entry->idx);
 188         hlist_add_head(&entry->node, &vmci_doorbell_it.entries[bucket]);
 189 
 190         spin_unlock_bh(&vmci_doorbell_it.lock);
 191 }
 192 
 193 /*
 194  * Remove the given entry from the index table.  This will release() the
 195  * entry's resource.
 196  */
 197 static void dbell_index_table_remove(struct dbell_entry *entry)
 198 {
 199         spin_lock_bh(&vmci_doorbell_it.lock);
 200 
 201         hlist_del_init(&entry->node);
 202 
 203         notify_idx_count--;
 204         if (entry->idx == max_notify_idx - 1) {
 205                 /*
 206                  * If we delete an entry with the maximum known
 207                  * notification index, we take the opportunity to
 208                  * prune the current max. As there might be other
 209                  * unused indices immediately below, we lower the
 210                  * maximum until we hit an index in use.
 211                  */
 212                 while (max_notify_idx > 0 &&
 213                        !dbell_index_table_find(max_notify_idx - 1))
 214                         max_notify_idx--;
 215         }
 216 
 217         last_notify_idx_released = entry->idx;
 218 
 219         spin_unlock_bh(&vmci_doorbell_it.lock);
 220 
 221         vmci_resource_put(&entry->resource);
 222 }
 223 
 224 /*
 225  * Creates a link between the given doorbell handle and the given
 226  * index in the bitmap in the device backend. A notification state
 227  * is created in hypervisor.
 228  */
 229 static int dbell_link(struct vmci_handle handle, u32 notify_idx)
 230 {
 231         struct vmci_doorbell_link_msg link_msg;
 232 
 233         link_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
 234                                             VMCI_DOORBELL_LINK);
 235         link_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
 236         link_msg.hdr.payload_size = sizeof(link_msg) - VMCI_DG_HEADERSIZE;
 237         link_msg.handle = handle;
 238         link_msg.notify_idx = notify_idx;
 239 
 240         return vmci_send_datagram(&link_msg.hdr);
 241 }
 242 
 243 /*
 244  * Unlinks the given doorbell handle from an index in the bitmap in
 245  * the device backend. The notification state is destroyed in hypervisor.
 246  */
 247 static int dbell_unlink(struct vmci_handle handle)
 248 {
 249         struct vmci_doorbell_unlink_msg unlink_msg;
 250 
 251         unlink_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
 252                                               VMCI_DOORBELL_UNLINK);
 253         unlink_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
 254         unlink_msg.hdr.payload_size = sizeof(unlink_msg) - VMCI_DG_HEADERSIZE;
 255         unlink_msg.handle = handle;
 256 
 257         return vmci_send_datagram(&unlink_msg.hdr);
 258 }
 259 
 260 /*
 261  * Notify another guest or the host.  We send a datagram down to the
 262  * host via the hypervisor with the notification info.
 263  */
 264 static int dbell_notify_as_guest(struct vmci_handle handle, u32 priv_flags)
 265 {
 266         struct vmci_doorbell_notify_msg notify_msg;
 267 
 268         notify_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
 269                                               VMCI_DOORBELL_NOTIFY);
 270         notify_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
 271         notify_msg.hdr.payload_size = sizeof(notify_msg) - VMCI_DG_HEADERSIZE;
 272         notify_msg.handle = handle;
 273 
 274         return vmci_send_datagram(&notify_msg.hdr);
 275 }
 276 
 277 /*
 278  * Calls the specified callback in a delayed context.
 279  */
 280 static void dbell_delayed_dispatch(struct work_struct *work)
 281 {
 282         struct dbell_entry *entry = container_of(work,
 283                                                  struct dbell_entry, work);
 284 
 285         entry->notify_cb(entry->client_data);
 286         vmci_resource_put(&entry->resource);
 287 }
 288 
 289 /*
 290  * Dispatches a doorbell notification to the host context.
 291  */
 292 int vmci_dbell_host_context_notify(u32 src_cid, struct vmci_handle handle)
 293 {
 294         struct dbell_entry *entry;
 295         struct vmci_resource *resource;
 296 
 297         if (vmci_handle_is_invalid(handle)) {
 298                 pr_devel("Notifying an invalid doorbell (handle=0x%x:0x%x)\n",
 299                          handle.context, handle.resource);
 300                 return VMCI_ERROR_INVALID_ARGS;
 301         }
 302 
 303         resource = vmci_resource_by_handle(handle,
 304                                            VMCI_RESOURCE_TYPE_DOORBELL);
 305         if (!resource) {
 306                 pr_devel("Notifying an unknown doorbell (handle=0x%x:0x%x)\n",
 307                          handle.context, handle.resource);
 308                 return VMCI_ERROR_NOT_FOUND;
 309         }
 310 
 311         entry = container_of(resource, struct dbell_entry, resource);
 312         if (entry->run_delayed) {
 313                 if (!schedule_work(&entry->work))
 314                         vmci_resource_put(resource);
 315         } else {
 316                 entry->notify_cb(entry->client_data);
 317                 vmci_resource_put(resource);
 318         }
 319 
 320         return VMCI_SUCCESS;
 321 }
 322 
 323 /*
 324  * Register the notification bitmap with the host.
 325  */
 326 bool vmci_dbell_register_notification_bitmap(u64 bitmap_ppn)
 327 {
 328         int result;
 329         struct vmci_notify_bm_set_msg bitmap_set_msg;
 330 
 331         bitmap_set_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
 332                                                   VMCI_SET_NOTIFY_BITMAP);
 333         bitmap_set_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
 334         bitmap_set_msg.hdr.payload_size = sizeof(bitmap_set_msg) -
 335             VMCI_DG_HEADERSIZE;
 336         if (vmci_use_ppn64())
 337                 bitmap_set_msg.bitmap_ppn64 = bitmap_ppn;
 338         else
 339                 bitmap_set_msg.bitmap_ppn32 = (u32) bitmap_ppn;
 340 
 341         result = vmci_send_datagram(&bitmap_set_msg.hdr);
 342         if (result != VMCI_SUCCESS) {
 343                 pr_devel("Failed to register (PPN=%llu) as notification bitmap (error=%d)\n",
 344                          bitmap_ppn, result);
 345                 return false;
 346         }
 347         return true;
 348 }
 349 
 350 /*
 351  * Executes or schedules the handlers for a given notify index.
 352  */
 353 static void dbell_fire_entries(u32 notify_idx)
 354 {
 355         u32 bucket = VMCI_DOORBELL_HASH(notify_idx);
 356         struct dbell_entry *dbell;
 357 
 358         spin_lock_bh(&vmci_doorbell_it.lock);
 359 
 360         hlist_for_each_entry(dbell, &vmci_doorbell_it.entries[bucket], node) {
 361                 if (dbell->idx == notify_idx &&
 362                     atomic_read(&dbell->active) == 1) {
 363                         if (dbell->run_delayed) {
 364                                 vmci_resource_get(&dbell->resource);
 365                                 if (!schedule_work(&dbell->work))
 366                                         vmci_resource_put(&dbell->resource);
 367                         } else {
 368                                 dbell->notify_cb(dbell->client_data);
 369                         }
 370                 }
 371         }
 372 
 373         spin_unlock_bh(&vmci_doorbell_it.lock);
 374 }
 375 
 376 /*
 377  * Scans the notification bitmap, collects pending notifications,
 378  * resets the bitmap and invokes appropriate callbacks.
 379  */
 380 void vmci_dbell_scan_notification_entries(u8 *bitmap)
 381 {
 382         u32 idx;
 383 
 384         for (idx = 0; idx < max_notify_idx; idx++) {
 385                 if (bitmap[idx] & 0x1) {
 386                         bitmap[idx] &= ~1;
 387                         dbell_fire_entries(idx);
 388                 }
 389         }
 390 }
 391 
 392 /*
 393  * vmci_doorbell_create() - Creates a doorbell
 394  * @handle:     A handle used to track the resource.  Can be invalid.
 395  * @flags:      Flag that determines context of callback.
 396  * @priv_flags: Privileges flags.
 397  * @notify_cb:  The callback to be ivoked when the doorbell fires.
 398  * @client_data:        A parameter to be passed to the callback.
 399  *
 400  * Creates a doorbell with the given callback. If the handle is
 401  * VMCI_INVALID_HANDLE, a free handle will be assigned, if
 402  * possible. The callback can be run immediately (potentially with
 403  * locks held - the default) or delayed (in a kernel thread) by
 404  * specifying the flag VMCI_FLAG_DELAYED_CB. If delayed execution
 405  * is selected, a given callback may not be run if the kernel is
 406  * unable to allocate memory for the delayed execution (highly
 407  * unlikely).
 408  */
 409 int vmci_doorbell_create(struct vmci_handle *handle,
 410                          u32 flags,
 411                          u32 priv_flags,
 412                          vmci_callback notify_cb, void *client_data)
 413 {
 414         struct dbell_entry *entry;
 415         struct vmci_handle new_handle;
 416         int result;
 417 
 418         if (!handle || !notify_cb || flags & ~VMCI_FLAG_DELAYED_CB ||
 419             priv_flags & ~VMCI_PRIVILEGE_ALL_FLAGS)
 420                 return VMCI_ERROR_INVALID_ARGS;
 421 
 422         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 423         if (entry == NULL) {
 424                 pr_warn("Failed allocating memory for datagram entry\n");
 425                 return VMCI_ERROR_NO_MEM;
 426         }
 427 
 428         if (vmci_handle_is_invalid(*handle)) {
 429                 u32 context_id = vmci_get_context_id();
 430 
 431                 if (context_id == VMCI_INVALID_ID) {
 432                         pr_warn("Failed to get context ID\n");
 433                         result = VMCI_ERROR_NO_RESOURCES;
 434                         goto free_mem;
 435                 }
 436 
 437                 /* Let resource code allocate a free ID for us */
 438                 new_handle = vmci_make_handle(context_id, VMCI_INVALID_ID);
 439         } else {
 440                 bool valid_context = false;
 441 
 442                 /*
 443                  * Validate the handle.  We must do both of the checks below
 444                  * because we can be acting as both a host and a guest at the
 445                  * same time. We always allow the host context ID, since the
 446                  * host functionality is in practice always there with the
 447                  * unified driver.
 448                  */
 449                 if (handle->context == VMCI_HOST_CONTEXT_ID ||
 450                     (vmci_guest_code_active() &&
 451                      vmci_get_context_id() == handle->context)) {
 452                         valid_context = true;
 453                 }
 454 
 455                 if (!valid_context || handle->resource == VMCI_INVALID_ID) {
 456                         pr_devel("Invalid argument (handle=0x%x:0x%x)\n",
 457                                  handle->context, handle->resource);
 458                         result = VMCI_ERROR_INVALID_ARGS;
 459                         goto free_mem;
 460                 }
 461 
 462                 new_handle = *handle;
 463         }
 464 
 465         entry->idx = 0;
 466         INIT_HLIST_NODE(&entry->node);
 467         entry->priv_flags = priv_flags;
 468         INIT_WORK(&entry->work, dbell_delayed_dispatch);
 469         entry->run_delayed = flags & VMCI_FLAG_DELAYED_CB;
 470         entry->notify_cb = notify_cb;
 471         entry->client_data = client_data;
 472         atomic_set(&entry->active, 0);
 473 
 474         result = vmci_resource_add(&entry->resource,
 475                                    VMCI_RESOURCE_TYPE_DOORBELL,
 476                                    new_handle);
 477         if (result != VMCI_SUCCESS) {
 478                 pr_warn("Failed to add new resource (handle=0x%x:0x%x), error: %d\n",
 479                         new_handle.context, new_handle.resource, result);
 480                 goto free_mem;
 481         }
 482 
 483         new_handle = vmci_resource_handle(&entry->resource);
 484         if (vmci_guest_code_active()) {
 485                 dbell_index_table_add(entry);
 486                 result = dbell_link(new_handle, entry->idx);
 487                 if (VMCI_SUCCESS != result)
 488                         goto destroy_resource;
 489 
 490                 atomic_set(&entry->active, 1);
 491         }
 492 
 493         *handle = new_handle;
 494 
 495         return result;
 496 
 497  destroy_resource:
 498         dbell_index_table_remove(entry);
 499         vmci_resource_remove(&entry->resource);
 500  free_mem:
 501         kfree(entry);
 502         return result;
 503 }
 504 EXPORT_SYMBOL_GPL(vmci_doorbell_create);
 505 
 506 /*
 507  * vmci_doorbell_destroy() - Destroy a doorbell.
 508  * @handle:     The handle tracking the resource.
 509  *
 510  * Destroys a doorbell previously created with vmcii_doorbell_create. This
 511  * operation may block waiting for a callback to finish.
 512  */
 513 int vmci_doorbell_destroy(struct vmci_handle handle)
 514 {
 515         struct dbell_entry *entry;
 516         struct vmci_resource *resource;
 517 
 518         if (vmci_handle_is_invalid(handle))
 519                 return VMCI_ERROR_INVALID_ARGS;
 520 
 521         resource = vmci_resource_by_handle(handle,
 522                                            VMCI_RESOURCE_TYPE_DOORBELL);
 523         if (!resource) {
 524                 pr_devel("Failed to destroy doorbell (handle=0x%x:0x%x)\n",
 525                          handle.context, handle.resource);
 526                 return VMCI_ERROR_NOT_FOUND;
 527         }
 528 
 529         entry = container_of(resource, struct dbell_entry, resource);
 530 
 531         if (!hlist_unhashed(&entry->node)) {
 532                 int result;
 533 
 534                 dbell_index_table_remove(entry);
 535 
 536                 result = dbell_unlink(handle);
 537                 if (VMCI_SUCCESS != result) {
 538 
 539                         /*
 540                          * The only reason this should fail would be
 541                          * an inconsistency between guest and
 542                          * hypervisor state, where the guest believes
 543                          * it has an active registration whereas the
 544                          * hypervisor doesn't. One case where this may
 545                          * happen is if a doorbell is unregistered
 546                          * following a hibernation at a time where the
 547                          * doorbell state hasn't been restored on the
 548                          * hypervisor side yet. Since the handle has
 549                          * now been removed in the guest, we just
 550                          * print a warning and return success.
 551                          */
 552                         pr_devel("Unlink of doorbell (handle=0x%x:0x%x) unknown by hypervisor (error=%d)\n",
 553                                  handle.context, handle.resource, result);
 554                 }
 555         }
 556 
 557         /*
 558          * Now remove the resource from the table.  It might still be in use
 559          * after this, in a callback or still on the delayed work queue.
 560          */
 561         vmci_resource_put(&entry->resource);
 562         vmci_resource_remove(&entry->resource);
 563 
 564         kfree(entry);
 565 
 566         return VMCI_SUCCESS;
 567 }
 568 EXPORT_SYMBOL_GPL(vmci_doorbell_destroy);
 569 
 570 /*
 571  * vmci_doorbell_notify() - Ring the doorbell (and hide in the bushes).
 572  * @dst:        The handlle identifying the doorbell resource
 573  * @priv_flags: Priviledge flags.
 574  *
 575  * Generates a notification on the doorbell identified by the
 576  * handle. For host side generation of notifications, the caller
 577  * can specify what the privilege of the calling side is.
 578  */
 579 int vmci_doorbell_notify(struct vmci_handle dst, u32 priv_flags)
 580 {
 581         int retval;
 582         enum vmci_route route;
 583         struct vmci_handle src;
 584 
 585         if (vmci_handle_is_invalid(dst) ||
 586             (priv_flags & ~VMCI_PRIVILEGE_ALL_FLAGS))
 587                 return VMCI_ERROR_INVALID_ARGS;
 588 
 589         src = VMCI_INVALID_HANDLE;
 590         retval = vmci_route(&src, &dst, false, &route);
 591         if (retval < VMCI_SUCCESS)
 592                 return retval;
 593 
 594         if (VMCI_ROUTE_AS_HOST == route)
 595                 return vmci_ctx_notify_dbell(VMCI_HOST_CONTEXT_ID,
 596                                              dst, priv_flags);
 597 
 598         if (VMCI_ROUTE_AS_GUEST == route)
 599                 return dbell_notify_as_guest(dst, priv_flags);
 600 
 601         pr_warn("Unknown route (%d) for doorbell\n", route);
 602         return VMCI_ERROR_DST_UNREACHABLE;
 603 }
 604 EXPORT_SYMBOL_GPL(vmci_doorbell_notify);